Available energy

Available Energy is a concept in thermodynamics that refers to the amount of energy that can be converted into work in a system. It is also known as exergy and is a measure of a system's energy that can be used to perform work.

Overview

The concept of available energy is rooted in the second law of thermodynamics, which states that not all energy in a system can be converted into work. Some energy is always lost as heat during the conversion process. The available energy of a system is the maximum amount of work that can be extracted from the system without violating the second law of thermodynamics.

Calculation

The available energy of a system can be calculated using the formula:

E_a = U - T_0S

where:

E_a is the available energy,

U is the internal energy of the system,

T_0 is the temperature of the environment, and

S is the entropy of the system.

This formula shows that the available energy of a system decreases as the entropy of the system increases. This is because an increase in entropy corresponds to a decrease in the orderliness of the system, which in turn reduces the amount of energy that can be converted into work.

Applications

The concept of available energy is used in many fields, including engineering, physics, and chemistry. It is particularly important in the design of energy conversion systems, such as power plants and engines, where the goal is to extract as much work as possible from a given amount of energy.

In environmental science, the concept of available energy is used to understand and quantify the energy flows in ecosystems. It helps to explain why some organisms are more successful than others in capturing and using energy from their environment.

See also

• Energy conversion efficiency
• Laws of thermodynamics
• Entropy
• Exergy